Phase Behavior of Athabasca Vacuum Bottoms + n-Alkane Mixtures

Abstract

Summary The phase behavior of Athabasca vacuum bottoms (ABVB), a 798.15+K (525+°C) boiling fraction comprising 32 wt% pentane asphaltenes +pentane mixtures, is elucidated using x-ray transmission tomography. These pseudobinary mixtures are models for the development of novel heavy-oil/bitumen production and refining processes. Depending on their overall composition, these mixtures are shown to exhibit three- and four-phase equilibria, including both expected (L1L2V) and unexpected (L2L3V) phase behavior separated by a small L1L2L3V zone. These multiphase equilibria provide challenges in production environments, where miscible flooding is typically desired, but afford new opportunities for the development of separation technologies in refining. Example phase diagrams are presented (pressure-temperature at constant composition and pressure-composition at constant temperature), which focus on the bubble pressure region where multiphase regions arise. Limited phase equilibria data sets for ABVB+heptane, decane, and dodecane are also presented so that trends for ABVB+alkane mixtures with the size of the alkane diluent can be explored. It is expected that these phase diagrams will provide useful insights to heavy-oil producers and refiners, in addition to providing a benchmark for testing phase-behavior models for these and related complex hydrocarbon mixtures.